package com.pactera.utils;

import org.apache.commons.codec.binary.Base64;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.security.SecureRandom;
import java.util.Objects;


public class AESUtils {

    private static final Logger log = LoggerFactory.getLogger(AESUtils.class);

    private AESUtils() {
    }

    private static final String KEY_ALGORITHM = "AES";
    private static final String DEFAULT_CIPHER_ALGORITHM = "AES/ECB/PKCS5Padding";// 默认的加密算法

    /**
     * AES 加密操作:UTF-8
     *
     * @param pwd       明文
     * @param secretKey 密钥
     * @author: liqingdian
     */
    public static String encrypt(String pwd, String secretKey) {
        return encrypt(pwd, secretKey, null);
    }

    /**
     * AES 加密操作
     *
     * @param pwd       明文
     * @param secretKey 密钥
     * @param charset   字符集
     * @author: liqingdian
     */
    public static String encrypt(String pwd, String secretKey, Charset charset) {
        try {
            charset = Objects.isNull(charset) ? StandardCharsets.UTF_8 : charset;
            Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);// 创建密码器
            byte[] byteContent = pwd.getBytes(charset);
            cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(secretKey, charset));// 初始化为加密模式的密码器
            byte[] result = cipher.doFinal(byteContent);// 加密
            return Base64.encodeBase64String(result);// 通过Base64转码返回
        } catch (Exception ex) {
            log.error(ex.getMessage(), ex);
        }
        return null;
    }

    /**
     * AES 解密操作:UTF-8
     *
     * @param pwd       密文
     * @param secretKey 密钥
     * @author: liqingdian
     */
    public static String decrypt(String pwd, String secretKey) {
        return decrypt(pwd, secretKey, null);
    }

    /**
     * AES 解密操作
     *
     * @param pwd       密文
     * @param secretKey 密钥
     * @param charset   字符集
     * @author: liqingdian
     */
    public static String decrypt(String pwd, String secretKey, Charset charset) {
        try {
            charset = Objects.isNull(charset) ? StandardCharsets.UTF_8 : charset;
            //实例化
            Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);
            //使用密钥初始化，设置为解密模式
            cipher.init(Cipher.DECRYPT_MODE, getSecretKey(secretKey, charset));
            //执行操作
            byte[] result = cipher.doFinal(Base64.decodeBase64(pwd));
            return new String(result, charset);
        } catch (Exception ex) {
            log.error(ex.getMessage(), ex);
        }
        return null;
    }

    /**
     * 生成加密秘钥
     *
     * @param key     令牌
     * @param charset 字符集
     * @author: liqingdian
     */
    private static SecretKeySpec getSecretKey(final String key, Charset charset) {
        //返回生成指定算法密钥生成器的 KeyGenerator 对象
        KeyGenerator kg = null;
        try {
            charset = Objects.isNull(charset) ? StandardCharsets.UTF_8 : charset;
            kg = KeyGenerator.getInstance(KEY_ALGORITHM);
            //AES 要求密钥长度为 128
            kg.init(128, new SecureRandom(key.getBytes(charset)));
            //生成一个密钥
            SecretKey secretKey = kg.generateKey();
            return new SecretKeySpec(secretKey.getEncoded(), KEY_ALGORITHM);// 转换为AES专用密钥
        } catch (Exception ex) {
            log.error(ex.getMessage(), ex);
        }
        return null;
    }
}
